Bowen, R. Sidney, Dave Dawson on Convoy Patrol.

Bowen's Dave Dawson "War Adventures Series" was marketed to the "older boy" audience (mid- to late-teenagers), many of whom would have, in the course of World War 2, moved on from reading the Bowen novels to taking part in actual hostilities after joining (or being drafted into) the military. Each of the series' 15 published titles followed the adventures of Dave Dawson, a young American of 18 or so, who had been trapped in Europe at the outbreak of World War 2. Early on (Dave Dawson at Dunkirk (1941)) Dawson escapes to Britain with Freddy Farmer, a slightly younger Englishman. Both join the Royal Air Force, with Dawson trained as a pilot and "now offering his life and his all in serving England's cause" (Freddy gets to be co-pilot). During the course of the series Dawson and Farmer serve on practically all war fronts, from Singapore to Libya, on the "Russian Front" and into the Pacific.

In an Internet appreciation entitled "Dave Dawson at Sixty" the Rev. Iain Richardson (who'd read the series as a youth) writes:
"This is not Stendahl, nor Tolstoy writing about war. It is wartime propaganda gone literate for boys. It is Tom Swift brought up to date with its fascination for the technical toys of the 1940s; with an added touch of the Hardy Boys in uniform for its cardboard characters and fast-paced, credible action, based on pluck plus luck. It's a formula series, but a good one. The war history is accurate, although it occasionally reveals how much information was kept back for postwar historians to divulge."
(As of Aug. 2007, the full "Dave Dawson at Sixty" article could be found at the impossibly long URL: http://72.14.253.104/search?q=cache:7pHwZtzYHfsJ:users.tellurian.com/bksleuth/infoB.htm+%22dave+dawson+at+Sixty%22+iain+macdonald&hl=en&ct=clnk&cd=1&gl=us)

Dave Dawson on Convoy Patrol was number 4 in the series. In this installment Dave and Freddy are based on the south coast of England and assigned to convoy escort duty (their warplane is a Catalina "flying boat" ). Along the way they unmask and eventually subdue a Nazi spy who had been operating in Britain. The novel's climax occurs over the English Channel when the "boys" locate a German "raider and her wolf-pack of U-boats" which had been lying in wait for an approaching Allied merchant convoy.